The majority of the ski areas in the United States use snow making machines throughout the season to provide complete snow coverage of the slope irrespective of natural snow accumulation. Due to the high cost of energy, there is a continuing need to reduce the cost of making artificial snow, particularly by reduced compressed air consumption. While the initial cost of equipment is high, the expense of operation is considerable.
Snow making apparatus in current use follows two basic forms. Snow making machines of the electric motor-driven fan type have a plurality of nozzles open to the circulation of fan-driven air passing axially through the front end of a cylindrical carrier for the fan and motor. Some compressed air may be fed with the water to the nozzle to facilitate the formation of ice crystals along with the fan induced flow.
The second form is a snow gun utilizing a mixing chamber into which is fed compressed air and water under pressure through separate lines. While low in initial cost, such snow guns are more expensive to operate in terms of the total energy required. The snow gun includes a snow making nozzle which functions to convert water from a hose into droplets and to insure that the droplets are substantially frozen before they hit the ground. The majority of snow gun designs utilize compressed air to both atomize a water stream and impress a high velocity to the water droplets so that they have enough time in the ambient air to freeze. This type of snow making apparatus exhibits several design advantages including light weight and portability, reliable operation and the ability to make snow at all subfreezing wet-bulb temperatures.
Prior known air/water snow guns are generally adjusted by throttling the water pressure to the gun at a hydrant located 50 to 100 feet away. Decreasing the water pressure entering the gun results in greater compressed air flows and generally a drier snow product.
It is applicant's theory that this is the combined result of producing a smaller water droplet in the snow making nozzle, and having less water to freeze in the snow making plume (at the exit of the nozzle). Producing a smaller droplet increases the surface area/volume ratio of the water, enhancing heat transfer rates, while decreasing the water volume decreases the overall heat that must be released from the plume to allow freezing. One of the biggest advantages of the air/water snow making gun is the ability to continually adjust the water droplet characteristics by adjusting the water pressure to the gun. This is especially important in ambient temperatures close to freezing since all other types of snow guns have difficulty in reliably generating small particles.
In the air/water snow gun type of snow making apparatus, the compressed air is very expensive and often consumes over twenty-five times as much energy as that required to provide the water to the snow gun. Since the snow produced is only frozen water, the compressed air is essentially wasted during the conversion process of water to ice particles. Further, there appears to be a limitation on present air/water snow guns or snow nozzles based on their reliance on compressed air flow to adjust the characteristics of the water droplets the result of which is to insufficiently mix compressed air/water flow, produce non-uniform droplets, and fail to make effective use of available water pressure to either atomize or distribute the water particles or both.
It is therefore an object of the present invention to provide a compressed air/water snow gun which minimizes the amount of compressed air required for unit volume of water converted to ice, which optimizes the mixing of compressed air/water flow, which produces uniform droplets under all snow making conditions, which makes effective use of available water pressure to atomize and/or distribute water particles, which adjusts water flow at the nozzle location instead of at a remote hydrant and which permits the use of the full pressure energy of the water stream in the atomization process.
It is a further object of the present invention to provide such an improved compressed air/water snow gun which forms a hollow jet of water injected at high velocity into compressed air streams aligned with the gun direction and passing on both sides of the hollow jet of water to effectively mix the air and water by maximizing the amount of shear forces between the compressed air and water to break up the water jet into droplets of uniform size, to adjust water droplet size independent of compressed air volume, and to employ the high velocity of the water stream passing through a narrow annulus to distribute the water droplets rather than primarily relying on compressed air as in the past.